Exercise 3: Does My System Kill Processes at Logout? — Possible Solution
==========================================================================

Where to look:

  $ grep -i KillUserProcesses /etc/systemd/logind.conf

  #KillUserProcesses=no      commented out: the distribution's
                             built-in default applies
  KillUserProcesses=yes      processes are killed at logout

A line that is commented out (starts with #) shows the default the
distribution ships. Drop-in files can also change it:

  $ ls /etc/systemd/logind.conf.d/ 2>/dev/null

And to see whether your user is set to linger:

  $ loginctl show-user $USER --property=Linger
  Linger=no

If screen sessions kept disappearing, check first:

  1. KillUserProcesses — if it's yes, logout kills the session scope,
     screen included. Ask an administrator to enable lingering
     (loginctl enable-linger yourname) or start screen outside the
     session scope:  systemd-run --user --scope screen -S work

  2. Whether the machine rebooted — sessions never survive a restart
     (check `uptime`; Chapter 3).

WHY THIS WORKS AS AN ANSWER
------------------------------
It shows how to read the real setting, including the difference between
a commented-out default and an explicit value, and gives the two most
likely explanations in a sensible order. Changing logind.conf needs
administrator rights.